Encapsulated alternating current solenoid

ABSTRACT

This disclosure relates to alternating current solenoids of the commercial industrial type, including a C-stack, a solenoid coil disposed within the C-stack and a plunger having a shank portion received within the coil passage, and wherein the conventional sideplates, baseplate, cover, backstop, assembly bolts or rivets and even the flanged coil bobbin may be eliminated. The C-stack and coil are encapsulated in a thermosetting resin block extending from the bight portion to the pole faces of the C-stack and between the C-stack and the coil, and the pole faces of the C-stack are exposed to allow abutment by the plunger. A cap encloses the operating spaced for the plunger head at the pole faces of the C-stack and is secured to the thermosetting resin block providing a completely enclosed solenoid unit. Vacuum encapsulation may be facilitated by utilizing an encapsulating cup which forms an integral part of the final product. The coil assembly is shown as having means for retaining, during the encapsulated process, electric terminals which are exposed in the final product for connecting the coil to a source of current.

United States Patent [72] Inventor Louis R. Conratll Lathrup Village,Mich. 211 Appl. No. 26,241 [22] Filed Apr. 7, 1970 [45] Patented Sept.14,197] [73] Assignee Detroit Coail Company Ferndale, Mich.Continuation-impart of application Ser. No. 854,691, Sept. 2, 1969.

[54] ENCAPSULATED ALTERNATING CURRENT SOLENOID 14 Claims, 9 DrawingFigs.

[52] US. Cl 335/243, 335/257, 335/260 [51] lnt.Cl ll0lf 7/10 [50] Fieldof Search 335/202, 243, 247, 248, 249,257, 260, 262, 278

[56] References Cited UNITED STATES PATENTS 2,803,789 8/1957 Stanton335/257 2,975,340 3/1961 Jencks et al. 335/248 3,305,808 2/1967 Widl335/243 3,331,042 7/l967 Erickson et al. 3,451,021 6/1969 AthertonPrimary Examiner-G. Harris AttorneyBurton and Parker ABSTRACT: Thisdisclosure relates to alternating current solenoids of the commercialindustrial type, including aC- stack, a solenoid coil disposed withinthe C-stack and a plunger having a shank portion received within thecoil passage, and wherein the conventional sideplates, baseplate, cover,backstop, assembly bolts or rivets and even the flanged coil bobbin maybe eliminated. The C-stack and coil are encapsulated in a thermosettingresin block extending from the bight portion to the pole faces of theC-stack and between the C-stack and the coil, and the pole faces of theC-stack are exposed to allow abutment by the plunger. A cap encloses theoperating spaced for the plunger head at the pole faces of the C-stackand is secured to the thermosetting resin block providing a completelyenclosed solenoid unit. Vacuum encapsulation may be facilitated byutilizing an encapsulating cup which forms an integral part of the finalproduct. The coil assembly is shown as having means for retaining,during the encapsulated process, electric terminals which are exposed inthe final product for connecting the coil to a source of current.

PATENTED sn 1 4 1911 3.605054 sum 2 OF 4 F'IG3 INVENTOR. 100/6 R. CO/VAA7H Maw/u A T TORNEVS PATENTEDSEPMIS?! 3.605054 saw u [1F 4 I'm-m! ll IIIll I 20 INVENTOR.

ATTdRNvs ENCAPSULATED ALTERNATING CURRENT SOLENOID FIELD OF INVENTIONThis invention relates to alternating current solenoids. Thisapplication is a continuation-in-part of applicationSer. No. 854,, 69l,filed Sept..2, I969.

DESCRIPTION OF THE PRIOR ART Conventional industrial alternating currentsolenoids include a laminated C-stack, a coil received within theC-stack,

and a plunger having a shank portion received for reciprocation in apassage in the coil. The plunger includes laterally extending armportions adapted to overlie and repeatedly impact the pole faces of theC-stack, tending to make the solenoid a self-destructing device. It hastherefore been an object of many improvements in the design ofalternating current solenoids to increase the useful life of thesolenoid by improving its structural integrity. Dust, moisture, andother foreign matter in the solenoid tend to decrease solenoid life, andtherefore many suggested improvements have been directed to the problemof sealing the solenoid assembly.

A conventional industrial solenoid includes a base member which supportsthe C-stack, sideplates overlying opposite sides of the laminatedC-stack, a backstop for the plunger resiliently connected to thesideplates, and a cover which may be secured directly to the device tobe actuated, or to the base member of the solenoid. The cover isnormally a metal enclosure, spaced from the solenoid assembly andadapted to prevent entry of foreign matter; but the cover generallyincreases the operating temperature of the solenoid, as it prevents freecirculation of air about the solenoid, thereby contributing to itsultimate failure. The solenoid coil conventionally comprises an assemblyof a flanged plastic bobbin upon and between the flanges of which thecoil wire is wound. The bobbin confines the coil turns and holds thecoil to its proper shape while at the same time providing a means formounting and retaining the coil in the C-stack. It should be noted thateach of the foregoing structural elements, viz., the sideplates, base,cover, assembly bolts or rivets, and the flanged bobbin, not only addsto the cost of the solenoid assembly, but requires additional assemblycosts.

Therefore it is an object of the alternating current solenoid of thisinvention to eliminate a number, if not all of these parts,, and therebyreduce cost, while providing a solenoid of improve structural integrityand as long or longer life than the prior art solenoids.

The prior art also discloses the utilization of dust closures or capsfor direct current solenoids, and the advantages of potting orencapsulating various electrical elements, including transformers,direct current solenoid coils, electromagnetic cores, and the stylus ofa phonograph. The problems inherent in an alternating current solenoidare however substantially different than in these devices, and thesolutions suggested by the prior art are not considered analogous. Indirect current solenoids, for example, the coils have been individuallyencapsulated and the purpose has been to seal the coil assembly, andthis does not improve substantially the structural integrity of theentire unit. Alternatively, in a transforrner,, there are no movingparts, and the assembly may be completely encapsulated without departingfrom the teaching of the prior art. Examples of these devices are shownin the following US. Pat. Nos.: 342,881, 2,731,607, 2,749,393,2,858,487, 3,082,359, 3,226,606, 3,341,939, 3,377,046.

SUMMARY OF THE INVENTION The alternating current solenoid of thisinvention eliminates the requirement for a separate cover member, andsecures the laminated C-stack and coil in a unitary integral assembly,without the requirement of a separate base plate, sideplates and relatedfasteners. The conventional flanged coil bobbin may also be eliminated.One embodiment of the alternating current solenoid of this inventionincludes a conventional laminated C-stack having a bight portion andopposed pole faces adjacent the distal ends, a solenoid coil disposedwithin the C-stack, and a conventional plunger having opposed armportions overlying the pole faces of the C-stack and a shank portionreceived within the passage provided in the coil. It will be understoodhowever, that modifications may be made to the C-stack, coil and plungerwithout departing from the purview of this invention.

The C-stack and coil in the alternating current solenoid of thisinvention are encapsulated in a thermosetting resin block which extendsfrom the bight'portion to the pole faces of the C-stack and between thecoil and the C-stack. The thermosetting resin block is therefore inintimate heat transfer contact with the C-stack and coil and secures theC-stack and coil in integral fixed relation. The pole faces of theC-stack are exposed at the end of the thermosetting resin blockpermitting the plunger to abut directly the pole faces. A passage isprovided in the thermosetting resin block between the pole faces of theC-stack and the bight portion, which is coaxially aligned with thepassage in the coil to receive the solenoid plunger. A

cap member received over the end of the plunger and secured.

to he thermosetting resin block provides a backstop for the plunger andresults in a completely enclosed solenoid unit for mounting on thedevice to be actuated. In the preferred embodiment of the invention, thethermosetting resin block has sufficient structural integrity to permitdirect securement of the solenoid, by securing the block to the deviceto be actuated.

The thermosetting resin rigid block therefore strengthens the laminatedC-stack to substantially increase the life of the solenoid. Further, inthe preferred embodiment, the thermosetting resin block permits heattransfer between the solenoid and the environment, eliminating theincrease in operating temperature resulting from the conventional metalenclosure. The fact that the laminated C-stack and the coil areencapsulated as a single unit, with the thermosetting resin providedboth around and between the C-stack and the coil, prevents relativemovement between these elements. The thermosetting resin block alsoeliminates the necessity for a baseplate in that the block may bedirectly secured to the device to be actuated, and replaces thesideplates without the requirement of additional bolts or securingmeans. The cap is secured directly to the block, and functions as abackstop for the plunger as described above.

In the disclosed embodiment of the alternating current solenoid of thisinvention, the cap includes a translucent portion, and the solenoidincludes a light connected in parallel with the coil, which indicateswhen the solenoid is energized. The cap is secured to the thermosettingresin blocks by bolts, two of which extend through the end of the block,adjacent the bight portion of the C-stack, to secure the solenoid to thedevice to be actuated. In one embodiment of the invention a pair of U-shaped clips are provided at opposite ends of the coil, and encapsulatedwith the C-stack and coil, to retain the electrical leads duringencapsulation, and the leads are encapsulated within the thermosettingplastic block. A manual actuator pin is also provided, within the cap,to permit manual actuation of the plunger without removal of the cap.Other advantages and meritorious features will more fully appear fromthe following description and claims, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation of oneembodiment of an alternating current solenoid of this invention,partially cross sectioned to show the internal structure;

FIG. 2 is a top cross-sectional view of the embodiment of the inventiondisclosed in FIG. I, in the direction of view arrows 2-2;

FIG. 3 is a cross-sectional view of the embodiments shown in FIG. I, inthe direction of view arrows 3-3, including a breakaway section;

FIG. 4 is a partial cross-sectional view of the embodiment of thesolenoid shown in FIG. 1, in the direction of view arrows 44;

FIG. 5 is a side elevation of another embodiment of an alternatingcurrent solenoid of this invention, partially cross sectioned to showthe internal structure;

FIG. 6 is a cross-sectional view taken on the line 66 of FIG. 5;

FIG. 7 is another side elevation of the embodiment of FIG. 5 partiallybroken away and partially in cross section, the sectional view beingtaken on the line 7--7 of FIG. 5; 8 of FIG. 8 is a cross-sectional viewtaken on the line 8-8 of FIG. 5; and

FIG. 9 is a cross-sectional schematic view of a mold for illustrating amethod of making a solenoid according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS solenoid armature or plunger24. Generally representative of these elements are the C-stacks, coilsand plungers disclosed in U.S. Pat. Nos. 2,466,592, 2,665,397 and2,671,187 to which reference may be made to supplement the descriptionwhich follows. In addition to these conventional elements, the solenoidincludes electric connector prongs 26 for connecting the coil to asource of electric power (not shown), a thermosetting resin block 28, acap 30 provided with a manual actuating pin 32, a light bulb 34 in thecap electrically connected in parallel with the coil 22, means 36securing the cap to the housing, and means 38 for securing the entiresolenoid to the device to be actuated (not shown) such as a hydraulicvalve.

The Cstack, formed of a plurality of soft iron laminations securedtogether by rivets, two of which are shown at 40, includes a bightportion 42 and opposed distal end portions 44. The bight portion isprovided with locating surface portions 46 which may simply comprise thelower outer surface of the bight portion as shown in FIGS. I and 3. Suchsurface portions are adapted to abut a surface of the device to beactuated to accurately locate the solenoid on such device. The bightportion is also provided with a central aperture 48 for the reception ofa pushpin or other actuatable member (not shown) which is adapted toabut the lower end of the shank portion 50 of the plunger, as isconventional, with the opposite end of the pushpin or actuatable memberadapted to cooperate with the device to be actuated for transmittingmotion from the plunger to such device. U.S. Pat. Nos. 2,975,340 and2,991,399 show representative pushpins in association with devices to beactuated and which may be referred to for further description of thisaspect of the present disclosure.

The distal ends 44 of the C-stack overlie in spaced relation the bightportion 42 and are provided at their upper surfaces, if desired, withshading coils 52, one of which is shown in FIG. 3. These upper surfacesprovide pole faces which the plunger abuts when the solenoid isenergized and the plunger has been drawn fully into the coil 22.

The plunger 24 comprises a plurality of soft iron laminations securedsecured together by a plurality of rivets 54, four of which are shown inFIG. 3. In addition to the shank portion 50 the plunger includesoppositely and laterally extending arm portions 56 together comprising ahead whichis adapted to overlie and abut the pole faces at the distalends of the C- stack. While the plunger shown is generally T-shapedplungers of different configuration may be utilized without departingfrom the scope of the invention. The lower end of the shank portion isprovided with a hardened steel insert 58 providing a wear surface toabut the pushpin or actuatable member heretofore mentioned. The lowersurface 60 of the shank is spaced slightly from the opposed surface 62of the bight of the C-stack when the plunger head abuts the pole facesto provide the usual airgap.

The coil 22 is wound on a bobbin 64 which includes a centralrectangularly shaped barrel portion 66 provided with laterally extendingflanges 68 and 70, the flange 68 being spaced from the upper end of thebarrel as shown in FIGS. 1 and 3, and with the coil wrapped about thebarrel between the flanges.

To connect the solenoid into an energizing circuit, prongs 26 areprovided. These prongs are adapted to be telescopically received incomplementary female sockets on the device to be actuated similar to thearrangement shown in FIGS. 13 and 14 of U.S. Pat. No. 2, 975, 340. Suchprongs comprise the downwardly projecting ends of a pair of pins 72 and74, which are connected to the ends of the wire of coil 22 in anysuitable fashion, such as by soldering. One end of the coil wire isshown in FIG. 1 connected at 25 to the pin 72. The other end of the coilwire (not shown) is connected in like fashion to the pin 74. The upperends of the pins are connected to opposite sides of the circuit for thelight bulb 34 as shown in FIG. 4, such connection being effected in anysuitable fashion such as by soldering. The circuit for the light bulbmay include a currentlimiting resistor 76. The bulb indicates by itsillumination that the coil is energized thereby helping to tracemalfunctions of the system in which the solenoid is used.

The interior of the barrel 66 of the bobbin provides a passageway forreceiving the shank of the plunger and it will be observed that suchpassageway extends from the pole faces of the C-stack to the bightportion thereof. If desired the bight portion of the C-stack may beprovided with a raised step 78 over which the lower end of the barrel istelescoped as shown in FIG. 1.

The C-stack, coil and bobbin, and the pins 72 and 74 are encapsulated ina thermosetting resin block 28. The resin of the block intimatelyengages the surfaces of the C-stack, coil and bobbin as well as the pinsand serves to integrate such parts into a solid, integral, blocklikeunit. The encapsulation of the C-stack, coil, bobbin, and pins may beeffected by transfer molding, vacuum molding or simple casting,utilizing a conventional epoxy resin which may be either a casting resinor molding resin utilizing a mineral filler. Either type resin givesgood thermal conductivity and adequate structural strength for thepurpose involved. However, other thermosetting resins may be foundsuitable. As continuous operation of the sole noid may involvetemperatures of approximately 105 C., the resin should be capable ofadequately withstanding such temperatures. When vacuum molding isemployed for encapsulation the resin material tends to impregnate thecoil and enter between the laminations of the C-stack, and as aconsequence results in a stronger construction than provided by therelatively low-pressure transfer molding operation or simple casting.With the bobbin 64 formed of nylon, the epoxy resin comprising thehousing will adhere to and become substantially integral therewith.

To hole the pins 72 and 74 in proper location prior to encapsulation, apair of generally C-shaped retaining members 80 and 82 may be utilizedwhich lie adjacent the bobbin flanges and embrace respectively thebarrel 66 of the bobbin, as shown in FIG. 2, and the step portion 78 ofthe C-stack as indicated in FIG. 3. These retaining members are providedwith pin-retaining notches 83 into which the pins are snapped at thetime of assembly of the components. The retaining members may be fonnedof any suitable sheet plastic lamination material. In lieu of theretaining members, the bobbin flanges 68 and 70 may be provided withextensions having pinretaining notches similar to the notches 83 and theretaining members 80 and 82 thereby eliminated.

In the disclosed embodiment the thermosetting resin block is providedwith a pair of tapped holes 84 and 86 at two opposite corners forreceiving screws 36 which extend through suitably provided holes in thecap 30 to retain the cap on the block. The block is also provided at theother opposite corners with through passages 88 and 90 for the receptiontherethrough of the screws 38 which are adapted to be threaded into thedevice to be actuated to mount the solenoid thereupon. While only thetwo screws 38 are shown for securing the solenoid to the device to beactuated, it will be understood that four screws may be provided forthis purpose, the two screws 36 being replaced by screws correspondingto screws "8 and suitable through passages therefor being provided inthe block. However, by providing the screws 36 the cap may be retainedon the block during handling of the solenoid apart from the device to beactuated.

The cap 30 may be formed of any suitable material. In the discloseembodiment the cap is formed of a material such as Delrin or Nylon whichmay be reinforced by suitable fillers if desired. The cap is interiorlyshaped to provide a plungerhead-receiving pocket 92 and an adjacentlight bulb receiving pocket 94 with an exterior wall 96 of the pocketbeing translucent or provided with a translucent window to allow thelight from the bulb to shine therethrough. The cap is further providedwith a cylindrical counterbore aperture 98 for the reception of themanual actuator pin 32. The pin may be provided with resilient O-rings100 and 102 with the latter serving to seal the pin in the aperture andwith the former serving to provide a resilient compressible membercushioning the shock of the backstroke of the plunger head as it strikesthe pin during upward movement. It will be understood that when the coil22 is energized the plunger is drawn to the position shown in FIGS. Iand 3 and when the coil is deenergized the device to be actuated,operating through the pushpin or actuatable member, shifts the plungerupwardly with it striking the manual actuator 32. Cushioning thisbackstroke of the plunger reduces the self-destructive action of thesolenoid.

While not shown, a suitable gasket may be provided at the interface 104between the cap and the block to provide a fluidtight enclosure, andanother gasket may be provided at the bottom surface 106 of the block toseal it against the device to be actuated, whereby oil may flow from thedevice to be actuated into the block and fluidtight integrity will bemaintained.

The resin block 28 extends from the bight portion locating face 46 tothe distal ends 44 of the C-stack with the locating face 46 and the polefaces at the opposite end of the C-stack being exposed such that thesolenoid may be accurately mounted on the device to be actuated and sothat the plunger head may directly abut the pole faces.

In FIGS. 5-8 another embodiment of the invention is shown. Suchembodiment differs from the one of FIGS. 1-4 essentially in that theflanged coil bobbin has been eliminated thereby allowing a greaternumber of coils turns and as a consequence greater force output for thesize of the solenoid is attainable. In this embodiment the solenoid ispotted in the resin block by vacuum casting and the finished productincludes an an integral part of the block, the cup within which theblock is cast. As many parts in this embodiment correspond with partshereinbefore described and a description thereof need not be repeated,such corresponding parts 'are identified by primed reference numerals.

The coil 110 is wound on a tube 112 and during the winding operation thewire may be coated, as is conventional during coil-winding operations,with a binder that holds the turns in position during the manufacturingoperation. The tube 112 may be of phenolic impregnated paper or thelike, whose length is such that one end 114 is received over the step78' at the bight portion of the C-stack and the opposite end 116 extendsupwardly somewhat between the opposed surfaces of the distal ends 44 ofthe C-stack. The C-shaped retaining members 80 and 82' are snappedontothe tube above and below the coil to hold the pins 72' and 74' asshown in FIGS. 5-8.

The potting material forming the block 116 intimately engages thesurfaces of the C-stack and surrounds the coil 110 and flows between thecoil and the C-stack, as at 118 in FIG. 7, and forms a liner 120 throughthe tube extending from the step 78' of the C-stack up between thedistal ends 44 thereof FIGS. 5-8 the block notonly extends about theoutside of the to guide the plunger. As a consequence, in the embodimentof 4 coil but also through the plunger-receiving passageway through thecoil and between the distal ends 44 of the C-stack and serves to betterintegrate the coil and C-stack. By selecting as the resin from which theblock is formed, one characterized by its lubricity and long wearingqualities, the liner I20 extending through the coil will accommodate thereciprocation of the plunger shank without the necessity of a separatecoil liner as is often utilized in the prior art.

Forming the embodiment of FIGS. 5-8 by vacuum casting improvesstructural integrity as the casting resin will better penetrate thesmall cracks or spaces of the C-stack and coil assembly. In thisconnection it is advantageous to perform the casting utilizing a cup 122within which the casting operating is performed and which will become anintegral part of the final product. The cup is a performed part whichmay be made of any suitable material such as phenolic resin. It may beinternally shaped to provide longitudinal pockets 124 and 126 forreceiving and centering the C-stack therein. The cup may also beprovided at each of its inside four corners with a fillet 128, with onepair of diagonally opposite fillets provided with longitudinalthrough-apertures 130 through which the bolts 38' may extend, and theremaining fillets threaded or adapted to threadedly receive the screws36 for retaining the cap 30'. The bottom 132 of the cup extends acrossthe top or end of the block 116 adjacent the pole faces of the stator,but with the pole faces exposed to the plunger, and the cap rests on thecup bottom as shown in FIG. 5. The bottom 132 of the cup may be providedwith cutouts to receive the distal ends, or pole faces, of the C-stackand also a molding plug, similar to the plug 134 of FIG. 9. Cutouts arealso provided in the cup bottom for receipt and location of the upperends of the pins 72 and 74'.

In the vacuum casting manufacture of the FIGS. 5-8 embodiment, the coilI10, and pin retainers 80' and 82 holding the pins, are assembled in theC-stack. Such assembly is then inserted in the cup. The cup with thesolenoid parts therein is next placed in a mold and a plug is insertedthrough the cup bottom and into the plunger passageway spaced slightlyfrom the inner wall surfaces of the tube I12, such as shown in FIG. 99.The end of the plug abuts the step 78 of the C-stack. Another portion ofthe mold extends through the pushpin aperture 48' and into abutment withthe plug 134. A vacuum is applied to the mold and to the cup and partstherein and the resin is introduced as at 142 to fill the cup and theinterstices of and around the parts therein. Upon solidification of theresin the mold is opened and the cup-encased block is removed.

As shown in FIGS. 5 and 7, the resin block may extend beneath the bightportion of the C-stack as at 144. In such event the lower surface of theresin block in relation to the C- stack must be held within closetolerances as such surface will become the locating face of the solenoidon the part to be actuated.

The molding process schematically shown in FIG. 9 is not intended to belimited to the use of the cup I22, in fact the cup is not specificallyshown in such Figure. Rather the Figure is intended to illustrate theinterfitting of the plug 134 in the plunger passageway as well as themold part 140 entering the actuating pin aperture 48 and 48'. Where aflanged bobbin as in FIG. I is utilized, the plug may fit the plungerpassageway in the bobbin sufficiently tightly so that the casting resinis completely excluded therefrom.

It is to be understood that while a flanged bobbin is not shown in theFIGS. 5-8 embodiment, such a bobbin may be utilized if desired. In otherwords, if the solenoid is to be manufactured utilizing the cup 122, abobbin of the character of bobbin 64 of FIGS. I-4 may be employed.Whether a conventional bobbin, or a bobbin such as shown in FIGS. 14 isutilized in the encapsulation operation or whether one omits a flangedbobbin and utilizes a tube such as the phenolic tube of FIGS. 5-8 willdepend upon various factors including the encapsulation temperature, thematerial of which the resin block is cast, the operating temperature ofthe solenoid, etc.

The use of cup 122 is particularly advantageous in the vacuum casting orencapsulation method as the cup effectively forms a liner for the moldthereby substantially reducing mold cleanup time. In addition, theinterior configuration of the cup for centering and positioning theC-stack and positioning the connector pins ensures accurate relationshipof the components of the final product in a simple and inexpensivefashion, and by utilizing different color cups color coding of the endproduct is attainable without the need of varying the color of thecasting resin.

What is claimed is:

1. An alternating current solenoid comprising, in combination: asolenoid C-stack having a bight portion and opposed pole faces adjacentthe distal ends, a solenoid coil disposed within the C-stack including acentral plunger-receiving passage, said C-stack and said coilencapsulated in a ther mosetting resin block extending from the bightportion to the pole faces of said C-stack and between the coil andC-stack, said thermosetting resin block in intimate heat transfercontact with and holding said coil and C-stack in integral fixedrelation, said pole faces of said C-stack being exposed for contact by aplunger, said thermosetting resin block having a passage between thepole faces of the C-stack and the bight portion coaxially aligned withthe passage in said coil, a plunger having opposed arm portionsoverlying said pole faces and shank portion received in said passage insaid coil for reciprocating movement therein, and a plunger-enclosingcap on the thermosetting resin block overlying the passage in said blockand providing a backstop for said plunger, said thermosetting resinblock and cap constituting a completely enclosed solenoid unit formounting on a device to be actuated, and said thermosetting resin blockhaving sufficient structural integrity to permit direct securement ofthe solenoid by securing said block to the device to be actuated.

2. The solenoid defined in claim 1, characterized in that the end of thebight portion of said C-stack has locating face portions exposed topermit accurate mounting of the solenoid on the device to be actuated.

3. The solenoid defined in claim 1, characterized in that said cap istranslucent and said solenoid includes illuminating means within saidcap connected to said coil and indicating when the solenoid isenergized.

4'. The solenoid defined in claim 1, characterized in that said cap issecured to the thermosetting resin block by bolts, at least two of whichextend through the end of the thermosetting resin block adjacent thebight portion of the C-stack to secure the solenoid to the device to beactuated.

5. The solenoid defined in claim 1, characterized in that said solenoidincludes a pair of electrical conductor retaining members encapsulatedwithin said thermosetting resin block, securing the electricalconductors of said solenoid during encapsulation.

6. The solenoid defined in claim 5, characterized in that said retainingmembers are generally C-shaped including a pair of arms disposed withinthe thermosetting resin block and a bight portion including an aperturereceiving the electrical conductors.

7. The solenoid defined in claim 6, characterized in that said retainingmembers are disposed adjacent the opposed ends of the coil, generallyperpendicular to the axis of the coil.

8. The solenoid defined in claim 1, characterized in that said capincludes an aperture generally coaxially aligned with theplunger-receiving passage and defines the walls thereof.

11. The invention as defined in claim 1, characterized in that said coilis wound on a flangeless tube, and said resin block encases the ends ofthe coil and extends along the plunger-receiving passage through thecoil defining the walls of such passage.

12. The invention defined in claim 1, characterized in that saidthermosetting resin block is surrounded by and contained in a cup withinwhich the block is cast and to which the block is intimately secured bythe casting operation.

13. A self-contained alternating current solenoid comprising, incombination: a solenoid C-stack, a solenoid coil in the C-stack, aplunger having a shank portion projecting into the coil and lateral armportions for abutting pole faces of the C- stack, an aperture in thebight portion of the C-stack for reception of a pushpin for operativeengagement with the plunger, electric connectors for connecting the coilto an energizing circuit, and a housing comprising a thermosetting resinblock encapsulating and structurally integrating the C- stack, coil andelectrical connectors as an operative assembly with the electricalconnectors exposed for connection to an external energizing circuit andwith the housing including an interiorly recessed end portion enclosingthe head of the plunger and providing clearance for reciprocationthereof, and means for connecting the housing to a device to beactuated.

14. A solenoid comprising, in combination: a C-stack, a solenoid coil inthe C-stack, a plunger having a shank portion received in the coil andan end portion projecting out of the coil between the distal ends of theC-stack, a housing enclosing the C-stack, coil and plunge r and having awall portion spaced from said end portion of the plunger when theplunger is sucked into the coil, a manual actuating pin reciprocablymounted in said wall portion of the housing and having a head disposedbetween such wall portion and said end portion of the plunger to beabutted thereby upon a backstroke of the plunger, and a resilientelement encircling said pin between the head and said wall portion tocushion the shock of the backstroke of the plunger striking the pin. 4

1. An alternating current solenoid comprising, in combination: asolenoid C-stack having a bight portion and opposed pole faces adjacentthe distal ends, a solenoid coil disposed within the Cstack including acentral plunger-receiving passage, said C-stack and said coilencapsulated in a thermosetting resin block extending from the bightportion to the pole faces of said Cstack and between the coil andC-stack, said thermosetting resin block in intimate heat transfercontact with and holding sAid coil and C-stack in integral fixedrelation, said pole faces of said C-stack being exposed for contact by aplunger, said thermosetting resin block having a passage between thepole faces of the C-stack and the bight portion coaxially aligned withthe passage in said coil, a plunger having opposed arm portionsoverlying said pole faces and shank portion received in said passage insaid coil for reciprocating movement therein, and a plunger-enclosingcap on the thermosetting resin block overlying the passage in said blockand providing a backstop for said plunger, said thermosetting resinblock and cap constituting a completely enclosed solenoid unit formounting on a device to be actuated, and said thermosetting resin blockhaving sufficient structural integrity to permit direct securement ofthe solenoid by securing said block to the device to be actuated.
 2. Thesolenoid defined in claim 1, characterized in that the end of the bightportion of said C-stack has locating face portions exposed to permitaccurate mounting of the solenoid on the device to be actuated.
 3. Thesolenoid defined in claim 1, characterized in that said cap istranslucent and said solenoid includes illuminating means within saidcap connected to said coil and indicating when the solenoid isenergized.
 4. The solenoid defined in claim 1, characterized in thatsaid cap is secured to the thermosetting resin block by bolts, at leasttwo of which extend through the end of the thermosetting resin blockadjacent the bight portion of the C-stack to secure the solenoid to thedevice to be actuated.
 5. The solenoid defined in claim 1, characterizedin that said solenoid includes a pair of electrical conductor retainingmembers encapsulated within said thermosetting resin block, securing theelectrical conductors of said solenoid during encapsulation.
 6. Thesolenoid defined in claim 5, characterized in that said retainingmembers are generally C-shaped including a pair of arms disposed withinthe thermosetting resin block and a bight portion including an aperturereceiving the electrical conductors.
 7. The solenoid defined in claim 6,characterized in that said retaining members are disposed adjacent theopposed ends of the coil, generally perpendicular to the axis of thecoil.
 8. The solenoid defined in claim 1, characterized in that said capincludes an aperture generally coaxially aligned with the passage insaid coil, and a manual actuator pin disposed in said aperture which maybe manually reciprocated to engage said plunger.
 9. The invention ofclaim 8 characterized further in that the manual actuator pin includes ahead portion disposed between the plunger and an opposed surface of thecap, and a resilient element encircling the pin and disposed between thehead thereof and said surface of the cap to cushion shock of the plungerstriking the pin.
 10. The invention defined by claim 1, characterized inthat a portion of the thermosetting resin block extends along theplunger-receiving passage and defines the walls thereof.
 11. Theinvention as defined in claim 1, characterized in that said coil iswound on a flangeless tube, and said resin block encases the ends of thecoil and extends along the plunger-receiving passage through the coildefining the walls of such passage.
 12. The invention defined in claim1, characterized in that said thermosetting resin block is surrounded byand contained in a cup within which the block is cast and to which theblock is intimately secured by the casting operation.
 13. Aself-contained alternating current solenoid comprising, in combination:a solenoid C-stack, a solenoid coil in the C-stack, a plunger having ashank portion projecting into the coil and lateral arm portions forabutting pole faces of the C-stack, an aperture in the bight portion ofthe C-stack for reception of a pushpin for operative engagement with theplunger, electric connectors for connecting the coil to an energizingcircuit, and a housIng comprising a thermosetting resin blockencapsulating and structurally integrating the C-stack, coil andelectrical connectors as an operative assembly with the electricalconnectors exposed for connection to an external energizing circuit andwith the housing including an interiorly recessed end portion enclosingthe head of the plunger and providing clearance for reciprocationthereof, and means for connecting the housing to a device to beactuated.
 14. A solenoid comprising, in combination: a C-stack, asolenoid coil in the C-stack, a plunger having a shank portion receivedin the coil and an end portion projecting out of the coil between thedistal ends of the C-stack, a housing enclosing the C-stack, coil andplunger and having a wall portion spaced from said end portion of theplunger when the plunger is sucked into the coil, a manual actuating pinreciprocably mounted in said wall portion of the housing and having ahead disposed between such wall portion and said end portion of theplunger to be abutted thereby upon a backstroke of the plunger, and aresilient element encircling said pin between the head and said wallportion to cushion the shock of the backstroke of the plunger strikingthe pin.